1. Field of Invention
The present invention relates to surveillance systems, and more particularly, to a method and system for detecting in real time a child's passage from a secure area.
2. Description of Related Art
According to statistics from the FBI's National Crime Information Center (NCIC), nearly 850,000 people are reported missing each year. Approximately 90% of those missing persons are under the age of eighteen, representing a total of about 725,000 annual juvenile cases. While many of these cases are quickly resolved, many others are abductions that often result in violence. In order to guard against such abductions, an increasing number of child tracking and child monitoring solutions are being marketed to parents.
Electronic detection systems are well known and have been applied to diverse applications. Such systems often include an indicator tag attached to a child to be detected by detection devices positioned near passageways for detection of an unauthorized passage of the child.
Child tracking and child monitoring systems are needed at public facilities such as retail stores, libraries, museums, theme parks, coliseums, stadiums, shopping centers, daycare centers and zoos. Some of these facilities have a multitude of obstructions, such as long and high counters with intervening aisles, large displays, walls separating rooms and numerous floors. A child could easily become lost in such an environment, in particular, amidst a multitude of shoppers. There is also the possibility that the child may become the victim of a kidnapping or abduction. The fact that the child is missing may not be detected for a substantial period of time because the parent may be engrossed in the shopping activity or believe that the child is safe. Unfortunately, the child may quickly separate from the parent by virtue of wandering or abduction.
The child monitoring systems that have had the most success to date in the mass market typically rely on global positioning satellite (GPS) technology. Known GPS locator tags, for example on a watch or backpack, provide satellite tracking capabilities to the wearer of the article. For a monthly fee, parents are able to access a GPS service provider's telephone number or website to request a locate of their child. This need to interface with a specific cellular telephone network is a glaring weakness of the GPS systems. If a child is located in an area where a server's provider's network provides no coverage, information can not be relayed to the central service and can not be made available to parents. In other words, areas without good network coverage create holes where tracking may not be successful. Another weakness with GPS centric systems is the potential difficulty to perform a locate indoors. Distributors of the GPS products indicate that the product is primarily intended for outdoor use.
Radio frequency identification (RFID) is surging in popularity as more and more uses for the technology are found. In early implementations, the technology was generally used for asset tracking in the shipping, manufacturing, retail and livestock industries. As wireless technologies infiltrate many segments of our society and prices of associated infrastructure decrease, it is more practical to look at RFID for other applications.
A basic RFID system consists of three components; an antenna or coil, a transceiver (with decoder), and a transponder (e.g., RF tag) electronically programmed with unique information. In a basic RFID system, the antenna emits radio signals to activate the tag and to read and write data to it. Antennas are the conduits between the tag and the transceiver, which controls the system's data acquisition and communication. Antennas can be placed at an entry/exit, for example, into or adjacent a door frame, to receive tag data from persons passing through the door. The electromagnetic field produced by an antenna can be constantly present, even when multiple tags are continually expected to pass. If constant interrogation is not required, the field can be activated as needed by a sensor device.
Often the antenna is packaged with the transceiver and decoder to become a reader (e.g., interrogator), which can be configured either as a hand-held or fixed mound device. The reader emits radio waves in ranges of from about one inch to over 100 feet, depending upon its power output and the radio frequency used. When an RFID tag passes through the electromagnetic zone of the reader, it detects the reader's activation signal. The reader decodes the tags data and the data is passed to a host computer for processing.
RFID tags are categorized as either active or passive. Active RFID tags are independently powered, generally by an internal battery, and are typically read/write devices (e.g., tag data can be rewritten and/or modified). An active tag's memory size varies to application requirements. In a typical read/write RFID system, a tag might give a machine a set of instructions, and the machine would then report its performance to the tag. This encoded data would then become part of the tagged part's history. The battery-supplied power of an active tag generally gives it a longer read range than a passive RFID tag, with the trade off of greater size, cost and a limited operational life.
Passive RFID tags operate without an internal power source and obtain operating power from the reader. Passive tags are consequently much lighter than active tags, less expensive, and offer a virtually unlimited operational lifetime period. The trade off is that passive RFID tags have shorter read ranges than active tags and require a higher powered reader. Read-only tags are typically passive and programmed with a unique set of data that can not be modified. Read-only tags typically operate as a license plate into a data base, in the same way linear bar codes reference a data base containing modifiable product-specific information.
RFID systems are also distinguished by their frequency ranges. Low-frequency systems (e.g., about 30 KHz to about 500 KHz) have shorter reading ranges and lower system costs. They are most commonly used in security access, asset tracking, and animal identification applications. High-frequency systems (e.g., about 850 MHz to about 950 MHz and about 2.4 GHz to about 2.5 GHz) offer reading ranges greater than about 90 feet and high reading speeds. Such systems are used for such applications as railroad car tracking and automated tow collection. However, the high performance of high-frequency RFID systems incurs higher system cost.
A significant advantage of RFID systems is the non-contact, non-line-of-sight nature of the technology. Packs can be read in visually and environmentally challenging conditions. RFID tags can also be read at remarkable speeds, in many cases responding in less than 100 milliseconds. For these reasons, RFID has become indispensable for a wide range of automated data collection and identification applications that would not be possible otherwise.
Another technology, known as Bluetooth Systems, is a short range wireless technology that originally was designed to replace infrared in mobile applications. Bluetooth technology can be used to allow multiple devices to interact with each other within a maximum range of 10 to 50 meters. Child tracking systems are used in the European market for amusement parks, shopping centers and zoos using Bluetooth readers and tags. However, there are key drawbacks of this technology. The limited range of the Bluetooth readers creates a need for more infrastructure than an RFID system, which translates into higher installation costs. Also, the Bluetooth technology does not provide a proactive solution for alerting parents to the location of a child. Parents must use their cellular telephone to initiate a short messaging service (SMS) to the Bluetooth system server in order to retrieve information. This requires cellular telephone service to be sufficient in the area from which the SMS is sent.
Another type of tracking system appears to have only the ability to track tags at an assigned location. It would be beneficial to track children using the same bracelet or wristband at any location where a system is installed to save money and make the use of the tags affordable.